Marco Rubio and the other GOP senators observed the Afghan army and had dinner with Afghan President Hamid Karzai.

WASHINGTON — Sen. Marco Rubio spent the weekend in Pakistan and Afghanistan and said he found encouraging signs, but he criticized the Obama administration's goal of beginning to withdraw U.S. troops this summer.

"I think we are on the timeline this year to have some real good news and make some significant progress," the Florida Republican said Monday in a conference call with reporters from Kabul. "But I think if you attach a date to it … you are really creating a difficult situation. The bad guys, the Taliban and even al-Qaida, must know all they have to do is wait."

President Barack Obama has doubled troops over the past two years but said a drawdown would begin this summer — straddling policy between those who want a harder line and those who think the United States needs to find a way out of a costly, deadly war that is more than 9 years old.

Increasingly, the government has been emphasizing presence until at least the end of 2014.

The success of driving out Taliban insurgents is a matter of dispute. A group of aid providers said last month that progress in southern Afghanistan is real but that insurgents gained a foothold elsewhere, disputing more upbeat U.S. assessments.

Rubio, 39, was making his first overseas trip as a senator (he traveled to Israel right after the election) and traveled with six other Republican senators, including Mitch McConnell. The trips are common for members of Congress.

The group met with U.S. Army Gen. David Petraeus, the commander of coalition forces; had dinner with Afghan President Hamid Karzai; and observed the Afghan National Army.

Coalition troops have been training the army so it can fully take over security. But it has been a struggle finding good men who stick with the regiment. Rubio said it can be as simple as some have never driven a vehicle.

"There is no way to overestimate how serious the challenge is, but we are headed in the right direction," Rubio said.

"One thing that's clear from these visits is that 2011 is going to be a critical year for Afghanistan security forces to step up and play a bigger role."

Criticizing what he called an "artificial timeline" of withdrawal, Rubio said the benchmark should be territories where the Afghans are successful in establishing security forces, courts and other government infrastructure.